Catalytically active body for the synthesis of dimethyl ether from synthesis gas

ABSTRACT

The invention relates to a catalytically active body for the synthesis of dimethyl ether from synthesis gas. In particular, the invention relates to an improved catalytically active body for the synthesis of dimethyl ether, whereby the components of the active body comprise a defined particle size distribution. Furthermore, the present invention concerns a method for the preparation of a catalytically active body, the use of the catalytically active body and a method for preparation of dimethyl ether from synthesis gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/598,931, filed Feb. 15, 2012, which is incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to a catalytically active body for the synthesisof dimethyl ether from synthesis gas. In particular, the inventionrelates to an improved catalytically active body for the synthesis ofdimethyl ether, whereby the components of the active body comprise adefined particle size distribution. Furthermore, the present inventionconcerns a method for the preparation of a catalytically active body,the use of the catalytically active body and a method for preparation ofdimethyl ether from synthesis gas.

BACKGROUND OF THE INVENTION

Hydrocarbons are essential in modern life and used as fuel and rawmaterials, including the chemical, petrochemical, plastics, and rubberindustry. Fossil fuels such as oil and natural gas are composed ofhydrocarbons with a specific ratio of carbon to hydrogen. In spite theirwide application and high demand, fossil fuels also have limitations anddisadvantages in the view of being a finite resource and theircontribution to global warming if they are burned.

Research on alternative fuels was mainly started due to ecological andeconomical considerations. Among the alternative fuels, dimethyl ether(DME), which is recently discovered as a clean fuel, can be synthesizedfrom syngas that was generated from different primary sources. Theseprimary sources can be natural gas, coal, heavy oil and also biomass. Upto now, only two DME synthesis procedures from synthesis gas have beenclaimed, whereby one is the traditional methanol synthesis, followed bya dehydration step and the other is a direct conversion of synthesis gasto DME in one single step.

Recently, attention has been directed towards the direct synthesis ofdimethyl ether from synthesis gas, using a catalytic system thatcombines a methanol synthesis catalyst and a catalyst for dehydration ofsaid alcohol. It was confirmed on the basis of experimental studies thatboth, the stage of methanol synthesis and the stage of methanoldehydration, could be conducted simultaneously on one appropriatecatalytic system. Depending upon the applied synthesis gas the catalystmight additionally show water gas shift activity.

Most known methods of producing methanol involve synthesis gas.Synthesis gas is a mixture of mainly hydrogen, carbon monoxide andcarbon dioxide, whereby methanol is produced out of it over a catalyst.CO+2H₂

CH₃OH

In a following step Methanol can be converted into DME by dehydrationover an acidic catalyst.2CH₃OH

CH₃OCH₃+H₂O

In the direct DME production there are mainly two overall reactions thatoccur from synthesis gas. These reactions, reaction (1) and reaction(2), are listed below.3CO+3H₂

CH₃OCH₃+CO₂   (1)2CO+4H₂

CH₃OCH₃+H₂O   (2)

Reaction (1) occurs with the combination of three reactions, which aremethanol synthesis reaction, methanol dehydration reaction, and watergas shift reaction:2CO+4H₂

2CH₃OH (methanol synthesis reaction)2CH₃OH

CH₃OCH₃+H₂O (methanol dehydration reaction)CO+H₂O

CO₂+H₂ (water gas shift reaction)

The reaction (1) has a stoichiometric ratio H₂/CO of 1:1 and has someadvantages over reaction (2). For example reaction (1) generally allowshigher single pass conversions and less energy-consuming in comparisonto the removal of water from the system in reaction (2).

Methods for the preparation of dimethyl ether are well-known from priorart. Several methods are described in the literature where DME isproduced directly in combination with methanol by the use of a catalystactive body in both the synthesis of methanol from synthesis gas andmethanol dehydration. Suitable catalysts for the use in the synthesisgas conversion stage include conventionally employed methanol catalystsuch as copper and/or zinc and/or chromium-based catalyst and methanoldehydration catalyst.

The document U.S. Pat. No. 6,608,114 B1 describes a process forproducing DME by dehydrating the effluent stream from the methanolreactor, where the methanol reactor is a slurry bubble column reactor(SBCR), containing a methanol synthesis catalyst that converts asynthesis gas stream comprising hydrogen and carbon monoxide into aneffluent stream comprising methanol.

Document WO 2008/157682 A1 provides a method of forming dimethyl etherby bimolecular dehydration of methanol produced from a mixture ofhydrogen and carbon dioxide, obtained by reforming methane, water, andcarbon dioxide in a ratio of about 3 to 2 to 1. Subsequent use of waterproduced in the dehydration of methanol in the bi-reforming processleads to an overall ratio of carbon dioxide to methane of about 1:3 toproduce dimethyl ether.

Document WO 2009/007113 A1 describes a process for the preparation ofdimethyl ether by catalytic conversion of synthesis gas to dimethylether comprising contacting a stream of synthesis gas, comprising carbondioxide with one or more catalysts active in the formation of methanoland the dehydration of methanol to dimethyl ether, to form a productmixture comprising the components dimethyl ether, carbon dioxide andunconverted synthesis gas, washing the product mixture comprising carbondioxide and unconverted synthesis gas in a first scrubbing zone with afirst solvent rich in dimethyl ether and subsequently washing theeffluent from the first scrubbing zone in a second scrubbing zone with asecond solvent rich in methanol to form a vapor stream comprisingunconverted synthesis gas stream with reduced content of carbon dioxidetransferring the vapor stream comprising unconverted synthesis gasstream with reduced carbon dioxide content for the further processing todimethyl ether.

Document WO 2007/005126 A2 describes a process for the production ofsynthesis gas blends, which are suitable for conversion either intooxygenates such as methanol or into Fischer-Tropsch-liquids.

The U.S. Pat. No. 6,191,175 B1 describes an improved process for theproduction of methanol and dimethyl ether mixture rich in DME fromessentially stoichiometrically balance synthesis gas by a novelcombination of synthesis steps.

In document US 2008/125311 A1 is a catalyst used for producing dimethylether, a method of producing the same, and a method of producingdimethyl ether using the same. More particularly, the present inventionrelates to a catalyst used for producing dimethyl ether comprising amethanol synthesis catalyst produced by adding one or more promoters toa main catalyst comprised of a Cu—Zn—Al metal component and adehydration catalyst formed by mixing Aluminium Phosphate (AlPO₄) withgamma alumina, a method of producing the same, and a method of producingdimethyl ether using the same, wherein a ratio of the main catalyst tothe promoter in the methanol synthesis catalyst in a range of 99/1 to95/5, and a mixing ratio of the methanol synthesis catalyst to thedehydration catalyst is in a range of 60/40 to 70/30.

The processes for the preparation of dimethyl ether according to theprior art bear the draw-backs that different steps have to be undergoneto get an efficient DME production. Besides this, the catalyst used inthe method known in prior art does not achieve the thermodynamicpossibilities. Therefore it is still desirable to increase the yield ofDME in the synthesis gas conversion.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a catalytically activebody that shows the ability to convert CO-rich synthesis gas selectivelyinto dimethyl ether and CO₂, whereby ideally the yield of the DME isincreased in comparison to the state of the art. If the conversion isincomplete, the resulting off-gas comprises hydrogen and carbon monoxidepreferably in the ratio H₂/CO˜1. Thus the off-gas can be recycleddirectly after the separation of the product DME and CO2. In addition,it is an object of the present invention to provide a method for thepreparation of a catalytically active body and a method for thepreparation of dimethyl ether from synthesis gas, comprising theinventive catalytically active body and also the use of thecatalytically active body.

These objects are achieved by a catalytically active body for thesynthesis of dimethyl ether from synthesis gas, comprising a mixture of:

-   -   (A) 70-90% by weight of a methanol-active component, selected        from the group consisting of copper oxide, aluminium oxide, zinc        oxide, amorphous aluminium oxide, ternary oxide or mixtures        thereof,    -   (B) 10-30% by weight of an acid component, selected from the        group consisting of alumosilicate, γ-alumina and zeolite or        mixtures thereof,    -   (C) 0-10 Gew.-% by weight of at least one additive, whereby the        sum of the components (A), (B) and (C) is in total 100% by        weight.

Preferably, the ternary oxide is a zinc-aluminium-spinel.

In a preferred embodiment of the catalytically active body the mixturecomprises:

-   -   (A) 70-90% by weight of a methanol-active component, selected        from the group consisting of copper oxide, aluminium oxide, zinc        oxide, amorphous aluminium oxide, ternary oxide or mixtures        thereof, whereby the component (A) has a particle size        distribution characterized by a D-10 value of 5-140 μm, a D-50        value of 40-300 μm, and a D-90 value of 180-800 μm,    -   (B) 10-30% by weight of an acid component, selected from the        group consisting of alumosilicate, γ-alumina and zeolite or        mixtures thereof, whereby the component (B) has a particle size        distribution characterized by a D-10 value of 5-140 μm, a D-50        value of 40-300 μm, and a D-90 value of 180-800 μm,    -   (C) 0-10 Gew.-% by weight of a at least one additive, whereby        the sum of the components (A), (B), and (C) is in total 100% by        weight and the particle size of components (A) and (B) is        maintained in the catalytically active body.

This particle size distribution can be determined via state of the artanalysis techniques, e.g. via analysis apparatus like Mastersizer 2000or 3000 by Malvern Instruments GmbH. The particle size distribution inthe sense of the invention is characterized by the D10-, D50-, and D-90value. The definition of D10 is: that equivalent diameter where 10 mass% (of the particles) of the sample has a smaller diameter and hence theremaining 90% is coarser. The definition of D50 and D90 can be derivedsimilarly (see: HORIBA Scientific, A Guidebook to Particle SizeAnalysis” page 6)

The inventive catalytically active body is characterized by a highturnover of carbon monoxide, preferably at 180° C. to 350° C. andparticular at 200° C. to 300° C. For example, a suitable pressure forthe synthesis of DME is preferably in the range from 20 to 80 bar and inparticular from 30 to 50 bar.

Preferably, the components (A) or (B) have a particle size distributioncharacterized by a D-10, D-50, and D-90 value of 5-80 μm, 40-270 μm, and250-800 μm respectively. In a further embodiment the particle sizedistribution from component (A) can be different from component (B) and(C), in particular, the components (A) or (B) have a particle sizedistribution characterized by a D-10, D-50, and D-90 value of 5-50 μm,40-220 μm, and 350-800 μm respectively. In a further embodiment theparticle size distribution from component (A) can be different fromcomponent (B) and (C).

In the sense of the present invention a catalytically active body can bea body known in the art that contains pores or channels or otherfeatures for enlargement of surface, which will help to bring the eductsin contact that they can react to the desired product. A catalyticallyactive body in the sense of the present invention can be understood as aphysical mixture, whereby the components (A) and (B) contact each otherand presenting channels and/or pores between their contact surfaces.Preferably, the components (A) and (B) are not melted or sintered attheir contact surfaces.

A methanol-active component in the sense of the present invention is acomponent which leads to the formation of methanol, starting fromhydrogen, carbon monoxide or carbon dioxide or mixtures thereof.Preferably, the methanol-active compound is a mixture of copper oxide,aluminium oxide and zinc oxide, whereby copper oxide can consist of allkinds of oxides of copper. In particular, copper has the oxidation state(I) or (II) in the oxide. The aluminium oxide according to the presentinvention can also be referred to γ-alumina or corundum, whereby zinc inzinc oxide in the sense of the present invention preferably has theoxidation state (II).

In a preferred embodiment of the catalytically active body, thecomponent (A) comprises 50-80% by weight of copper oxide, 15-35% byweight of ternary oxide and 15-35% by weight of zinc oxide and the sumof which is in total 100% by weight. In particular the component (A)comprises 65-75% by weight of copper oxide, 20-30% by weight of ternaryoxide and 20-30% by weight of zinc oxide and the sum of which is intotal 100% by weight.

In a preferred embodiment of the catalytically active body, thecomponent (A) comprises 50-80% by weight of copper oxide, 2-8% by weightof boehmite and 15-35% by weight of zinc oxide and the sum of which isin total 100% by weight. In particular the component (A) comprises65-75% by weight of copper oxide, 3-6% by weight of boehmite and 20-30%by weight of zinc oxide and the sum of which is in total 100% by weight.

In a preferred embodiment of the catalytically active body, thecomponent (A) comprises 50-80% by weight of copper oxide, 2-8% by weightof amorphous aluminium oxide and 15-35% by weight of zinc oxide and thesum of which is in total 100% by weight. In particular the component (A)comprises 65-75% by weight of copper oxide, 3-6% by weight of amorphousaluminium oxide and 20-30% by weight of zinc oxide and the sum of whichis in total 100% by weight.

In a preferred embodiment of the catalytically active body, thecomponent (A) comprises 50-80% by weight of copper oxide, 2-8% by weightof aluminium oxide and 15-35% by weight of zinc oxide and the sum ofwhich is in total 100% by weight. In particular the component (A)comprises 65-75% by weight of copper oxide, 3-6% by weight of aluminiumoxide and 20-30% by weight of zinc oxide and the sum of which is intotal 100% by weight.

In the sense of the present invention an acid component (B) is selectedfrom the group consisting of aluminosilicate, γ-alumina and zeolite ormixtures thereof. Aluminosilicate comprise minerals composed ofaluminium, silicon and oxygen. They are the major components of kaolinand other clay minerals like for example Halloysite, Kaolinite, Illite,Montmorillonite, Vermiculite, Talc, Palygorskite, Pyrophyllite, whichare also suitable as component (B).

In a preferred embodiment, the zeolite comprises 35-55% by weight ofsilicon, 0.15-4% by weight of aluminium, 45-65% by weight of oxygen andwhere appropriate 0-0.3 by weight of sodium and the sum of which is intotal 100% by weight. Preferably the zeolite comprises 40-52% by weightof silicon, 0.8-3.5% by weight of aluminium, 50-60% by weight of oxygenand where appropriate 0-0.3% by weight of sodium and the sum of which isin total 100% by weight. In a preferred embodiment zeolite can beZeolithe A, Zeolithe X, Zeolithe Y, Zeolithe L, Mordenit, ZSM-5, ZSM-11.

In the sense of the present invention an additive (C) can be astructure-promoter like but not limited a thermally decomposablecompound like polymers, wood dust, flour, graphite, film material, apainting, straw, strearic acid, palmitic acid, celluloses or acombination thereof. For example, the structure-promotor can help tobuild up pores or channels.

In a preferred embodiment the catalytically active body consists of (A)70-90% by weight of a methanol-active component and 10-30% by weight ofa zeolite (B) and the sum of (A) and (B) being in total 100% by weight.Preferably the catalytically active body consists of (A) 75-85% byweight of a methanol-active component and 15-25% by weight of a zeolite(B) and the sum of (A) and (B) being in total 100% by weight. Oneadvantage of this composition is that the turnover of the reaction ofthe methanol-active compound (A) and the acid compound (B) is favored,because the highly integrated catalyst system combines the methanolsynthesis, water gas shift activity, and methanol dehydration catalystin a close proximity. Therefore an optimum efficiency can be obtained.

In a preferred embodiment the catalytically active body is a pellet witha size in the range from 1×1 mm to 10×10 mm, preferably in the rangefrom 2×2 mm to 7×7 mm. The pellet is obtained by pressing the mixture ofthe components (A), (B) and (C) to a pellet. In the sense of the presentinvention a pellet can be obtained by pressing the components (A), (B)and optionally (C) under force to the pellet, whereby the shape of thepellet can be ring-shaped, star-shaped or spherical-shaped. Furthermorethe pellet can be hollow strings, triloops, multihole pellets,extrudates and alike.

The present invention further relates to a method for the preparation ofa catalytically active body, comprising the step:

-   -   c) preparation a physical mixture comprising:        -   (A) 70-90% by weight of a methanol-active component,            selected from the group consisting of copper oxide,            aluminium oxide, zinc oxide, amorphous aluminium oxide,            ternary oxide or mixtures thereof,        -   (B) 10-30% by weight of an acid component, selected from the            group consisting of alumosilicate, γ-alumina and zeolite or            mixtures thereof,        -   (C) 0-10 Gew.-% by weight of a at least one additive,            whereby the sum of the components (A), (B) and (C) is in            total 100% by weight.

In this context, the meanings of the features are the same as for thecatalytically active body already mentioned.

In the sense of the present invention preparing a physical mixture meansthat the different compounds (A), (B) and (C) are brought in contactwithout further chemical modification.

In a preferred embodiment of the method, the component (A) has aparticle size distribution characterized by a D-10 value of 5-80 μm, aD-50 value of 40-270 μm, and a D-90 value of 250-800 μm, whereby thecomponent (B) has a particle size distribution characterized by a D-10value of 5-80 μm, a D-50 value of 40-270 μm, and a D-90 value of 250-800μm and the particle size distribution of components (A) and (B) ismaintained in the catalytically active body. In a particular embodimentof the method, the component (A) has a particle size distributioncharacterized by a D-10 value of 5-50 μm, a D-50 value of 40-220 μm, anda D-90 value of 350-800 μm, whereby the component (B) has a particlesize distribution characterized by a D-10 value of 5-50 μm, a D-50 valueof 40-220 μm, and a D-90 value of 350-800 μm and the particle sizedistribution of components (A) and (B) is maintained in thecatalytically active body.

In a preferred embodiment the method comprising further the steps:

-   -   a) precipitation a copper-, zinc-, or aluminiumsalt or a mixture        thereof,    -   b) calcination of the product obtained in step a).

Preferably, the steps a) and b) are carried out before the step c).Preferably, the obtained product consists after step c) of 70-90% byweight of a methanol-active component (A), selected from the groupconsisting of copper oxide, aluminium oxide and zinc oxide or mixturesthereof, 10-30% by weight of an acid component (B), selected from thegroup consisting of alumosilicate, γ-alumina and zeolite or mixturesthereof. Preferably, after step c) the component (A) has a particle sizedistribution characterized by a D-10 value of 5-140 μm, a D-50 value of40-300 μm, and a D-90 value of 180-800 μm and the component (B) has aparticle size distribution characterized by a D-10 value of 5-140 μm, aD-50 value of 40-300 μm, and a D-90 value of 180-800 μm.

Preferably, the method comprises at least spray drying, filtration,grinding, sieving or further steps, known in the art to create acatalytically active body, or combinations thereof.

In the sense of the present invention precipitation is a method for theformation of a solid in a solution or inside another solid during achemical reaction or by diffusion in a solid. The precipitationtechniques are known in the art, see also Ertl, Gerhard, Knözinger,Helmut, Schüth, Ferdi, Weitkamp, Jens (Hrsg.) “Handbook of HeterogeneousCatalysis” 2nd edition 2008, Wiley VCH Weinheim, Vol. 1, chapter 2. Forexample salts of copper, zinc or aluminium are dissolved in a solvent,in particular water. At least two of the salts of either copper, zinc,or aluminium can be heated and a basic solution can be prepared andadded. Both solutions can be added in parallel to the template, till thesalt-solution is consumed. After this the suspension is vacuumed, dried,and calcinated under air flow.

Preferred anions in the salts for copper, zinc, or aluminium areselected from the group consisting of nitrate, acetate, halide,carbonate, nitrite, sulfate, sulfite, sulfide, phosphate ion orsilicate. In particular, salts of copper, zinc or aluminium formed withthe above mentioned anions can be converted into oxides of copper, zincor aluminium applying a calcination step.

Calcination in the sense of the present invention can be understood as athermal treatment process applied to ores and other solid materials tobring about a thermal decomposition, phase transition, or removal of avolatile fraction. The calcination process normally takes place attemperatures below the melting point of the product materials. Mostly itis done under oxygen-containing atmosphere. In some cases thecalcination can be performed under inert atmosphere (e.g. nitrogen).Calcination is to be distinguished from roasting, in which more complexgas-solid reactions take place between the furnace atmosphere and thesolids.

In particular the components (A), (B) and (C) can be compacted in apresser, a squeezer, a crusher or a squeezing machine, preferably afterstep a), b) or c). Compacting in the sense of the present invention canmean that particles of a defined particle size distribution are pressedto bodies, which have a diameter in the range of 1 to 10 mm and a heightof 1 to 10 mm. Preferably the particle size distribution is still leftafter the compacting.

In a preferred embodiment of the method a pellet is formed, preferablywith a size in the range from 1×1 mm to 10×10 mm, especially in therange from 2×2 mm to 7×7 mm.

In a preferred embodiment of the method, the components (A) and (B) areindependently pressed through at least one sieve, whereby the sieveexhibits a mesh size from 0.005 to 5 mm in order to obtain a particlesize distribution characterized by a D-10 value of 5-140 μm, a D-50value of 40-300 μm, and a D-90 value of 180-800 μm. Preferably the sieveexhibits a mesh size from 0.005 to 1.50 mm and in particular a mesh sizefrom 0.005 to 0.80 mm. In particular the particles can also exhibitparticle size distribution characterized by a D-10, D-50, and D-90 valueof 5-140 μm, 40-300 μm, and 180-800 μm respectively. Thereby thecomponents (A) and (B) can be obtained as particles with a definedparticle size distribution, also referred in the sense of the presentinvention as a split-fraction. Because of this split-fraction theCO-conversion increases when synthesis gas contacts the split-fraction.Furthermore the yield of the DME increases, when synthesis gas isconverted to DME by the catalytically active body. Preferably, this stepis included in step c).

In a further embodiment component (C) is admixed to the components (A)and (B) before sieving.

In a preferred embodiment of the preparation of a catalytically activebody at least three different sieves are used, whereby the components(A) and (B) are pressed in direction from the sieve with the biggestmesh size to the sieve with the smallest mesh size. By using threesieves with different mesh sizes the components (A) and (B) areinitially pressed into the sieve with the biggest mesh size, whichresults in particles with the maximal size of the mesh size of thissieve. Preferably, the particle size distribution of the components (A)and (B) is characterized by a D-10 value of 5-140 μm, a D-50 value of40-300 μm, and a D-90 value of 180-800 μm. These particles can also bebroken during the first sieving, so that smaller particles are obtained,which can go through the second sieve, which exhibits a smaller meshsize. Therefore a first fraction with a specific particle sizedistribution can be obtained before the second sieve. This fraction canalso be used as a catalytically active body. Besides this, the particleswhich go through the second sieve with a mesh size smaller than thefirst sieve, but bigger than the third sieve, can be obtained behind thesecond sieve and before the smallest sieve with the smallest mesh size.Also here the particles obtained after the second (middle) sieve can beused as a catalytically active body. In addition to this, the particlesobtained after the sieve with the biggest mesh size could be pressedthrough the second sieve in order to reduce the particle size.

In a preferred embodiment of the method according to the presentinvention in step a) a part of the component (A) is prepared byprecipitation reaction and/or calcination. In the sense of the presentinvention precursors of the component (A) in form of a salt in asolution can be heated and adjusted to a defined pH-value. After this, acalcination step can be carried out, whereby calcination is known fromprior art. These steps can lead to the desired component (A).

In a preferred embodiment of the inventive method at least one part ofcomponent (A) is precipitated and whereby at least another part ofcomponent (A), which is not subjected to the first precipitation, isadded to the precipitate. Preferably, it is added by spray drying orprecipation.

In a preferred embodiment of the inventive method, the method furthercomprises the step d) adding a mixture of hydrogen and nitrogen tocomponent (A) and/or (B). Preferably the content of the volume of thehydrogen is less than 5% in the mixture.

The present invention further relates to a method for the preparation ofdimethyl ether from synthesis gas comprising at least the steps:

-   -   e) reducing the catalytically active body    -   f) contacting the catalytically active body in a reduced form        with hydrogen and at least one of carbon monoxide or carbon        dioxide.

In a further embodiment the method comprising the steps:

-   -   g) providing the inventive catalytically active body, in        particular in form of pellets    -   h) disposing the catalytically active body in a reactor,    -   i) reducing the catalytically active body at a temperature        between 140° C. and 240° C. with at least a nitrogen and        hydrogen mixture.

The present invention further relates to the use of a catalyticallyactive body according to the present invention for the preparation ofdimethyl ether. Preferred admixtures and preferred methods for thepreparation are mentioned above and also included in the use.

The present invention is further illustrated by the following examples:

A) Synthesis of the Methanol-Active Compounds:

1. Example

Two solutions are prepared for the precipitation of the components:

Solution 1: A solution of 1.33 kg copper nitrate, 2.1 kg zinc nitrateand 0.278 kg aluminium nitrate are solved in 15 L water.

Solution 2: 2.344 kg sodium bicarbonate is dissolved in 15 L water.

Precipitation:

Both solutions are separately heated to 90° C., followed by the fastaddition of solution 1 to solution 2 within 1-2 minutes under stirring.Afterwards 15 min is stirred and the precipitation is filtered andwashed with water till it is free of nitrates. The filter cake is driedat 110° C. and is calcinated for 4 h at 270° C. under nitrogenatmosphere. The metal content of the catalyst is in atom-%: Cu 38.8; Zn48.8 and Al 12.9.

2. Example

Two solutions are prepared for the precipitation of the components:

Solution 1: A solution of 2.66 kg copper nitrate, 1.05 kg zinc nitrateand 0.278 kg aluminium nitrate are solved in 15 L water.

Solution 2: 2.344 kg sodium bicarbonate is dissolved in 15 L water.

Precipitation:

The same procedure as described in the 1. Example, whereby the metalcontent of the catalyst is in atom%: Cu 61.6; Zn 28.1 and Al 10.9.

3. Example-Preparation of Me30:

i. Precipitation:

A sodium bicarbonate solution (20%) is prepared, whereby 11 kg sodiumbicarbonate is dissolved in 44 kg demineralised water. Also aZn/Al-solution is prepared consisting of 6.88 kg zinc nitrate and 5.67kg aluminium nitrate and 23.04 kg water. Both solutions are heated to70° C. A template filled with 12.1 L demineralised water is also heatedto 70° C. Both solutions are added in parallel to the template at apH=7, till the Zn/Al-solution is consumed. Afterwards 15 h is stirred ata pH=7. After this the suspension is vacuumed and washed to a content ofsodium oxide<0.10% and the water is free of nitrate. The product isdried for 24 h at 120° C. and calcinated for 1 h at 350° C. under airflow.

ii. Precipitation:

A sodium bicarbonate solution (20%) is prepared, whereby 25 kg sodiumbicarbonate is dissolved in 100 kg demineralised water. Also aCu/Zn-nitrate solution is prepared consisting of 26.87 kg copper nitrateand 5.43 kg zinc nitrate and 39 kg water. Both solutions are heated to70° C. After the Cu/Zn-nitrate solution has reached a temperature of 70°C., the product of the 1.precipitation is added slowly and the pH-valueis adjusted to pH=2. Also a solution of nitric acid (65%) is provided(650 g conc. HNO₃ and 350 g demineralised water). A template filled with40.8 L demineralised water is also heated to 70° C. Both solutions(sodium bicarbonate and Cu/Zn-nitrate solution) are added in parallel tothe template at a pH=6.7, till the Cu/Zn-nitrate solution is consumed.Afterwards 10 h is stirred whereby the pH-value is adjusted to pH=6.7with the nitric acid (65%). After this the suspension is vacuumed andwashed to a content of sodium oxide<0.10% and the water is free ofnitrate. The product is dried for 72 h at 120° C. and calcinated for 3 hat 300° C. under air flow. After cooling to room temperature thematerial is ready for use.

B) Preparation of the Final Catalytically Active Body:

The methanol-active compound and the acid compound are compactedseparately in a tablet press and/or pelletizing machine. The obtainedmolding (diameter=ca, 25 mm, height=ca, 2 mm), is squeezed throughsieves with an appropriate mesh size, so that the desired split fractionis obtained. From both fractions the proper quantity is weight in (9/1,8/2, or 7/3 methanol-active/acidic compound) and mixed with the othercompound in a mixing machine (Heidolph Reax 2 or Reax 20/12).

C) Testing Conditions for Non-Pelletized Mixtures:

The catalytically active body (5 cm³ by volume) is incorporated in atubular reactor (inner diameter 0.4 cm, bedded in a metal heating body)on a catalyst bed support consisting of alumina powder as layer of inertmaterial and is pressure-less reduced with a mixture of 1 Vol.-% H₂ and99 Vol.-% N₂. The temperature is increased in intervals of 8 h from 150°C. to 170° C. and from 170° C. to 190° C. and finally to 230° C. At atemperature of 230° C. the synthesis gas is introduced and heated within2 h up to 250° C. The synthesis gas consists of 45% H₂ and 45% CO and10% inert gas (argon). The catalytically active body is run at an inputtemperature of 250° C., GHSV of 2400 h⁻¹ and a pressure of 50 bar.

D) Testing Conditions for Pelletized Mixtures:

Tests for pelletized materials are conducted in a similar test rickcompared to the setup described above for non-pelletized materials usingthe same routine. Only no tubular reactor with an inner diameter of 0.4cm is used but a tubular reactor having an inner diameter of 3 cm. Testsfor pelletized materials are done with a catalyst volume of 100 cm³.

Results:

According to table 1 the different mixtures are listed.

Methanol-Active Component:

Me30: Consists of 70% by weight of CuO, 5.5% by weight Al₂O₃ and 24.5%by weight of ZnO.

Acid Component:

The applied acid components have the following composition:

ZSM5-400H Al 0.23 g/100 g Na 0.09 g/100 g Si 45.5 g/100 g ZSM5-100H Al0.84 g/100 g Na 0.02 g/100 g Si  44 g/100 g ZSM5-80H Al 0.99 g/100 g Na<0.01 g/100 g  Si  44 g/100 g ZSM5-50H Al  1.7 g/100 g Na 0.02 g/100 gSi  43 g/100 g ZSM5-25H Al  2.7 g/100 g Na 0.16 g/100 g Si  41 g/100 g

In the following table 1 the results are presented. Me30 and ZSM5(corresponds to ZSM-5) with different ratios of Al, Na and Si are used.The different mixtures of split-fractions (the corresponding D-10, D-50,and D-90 values of Me30 and ZSM5-100H are presented in table 2) showdifferent CO-conversions. The comparison experiments C1 to C7 showing alower turnover, whereby the inventive experiments E1 and E2 showing anincreased value. Surprisingly the mixtures of inventive materialsshowing a particle size distribution that is characterized by a D-10,D-50, and D-90 value of 5-140 μm, 40-300 μm, and 180-800 μm,respectively, show a significantly increased CO-conversions compared tothe comparison experiments C1 to C7. With respect to the selectivitypatterns it is worth to mention that within the DME forming samples anequal selectivity of DME and CO₂ can be observed. This shows that allcatalysts have a sufficient water gas shift activity that is needed toconvert the water generated in the Methanol dehydration step with COinto CO₂. Furthermore all catalysts show an adequate MeOH dehydrationcapability apart from C4. This can be seen in the MeOH contents in theproduct streams in table 1.

Inventive experiment E3 shows that the superior performance of E1 ismaintained if this mixture is properly transferred into a pellet.

TABLE 1 Split- CO conversion Experiment Mixture (A):(B) fraction [%]S(MeOH) S(DME) S(CO₂) S(Others) C1 Me30:ZSM5-25H 0.05-0.1 38.5 2.4648.45 48.7 0.39 8:2 C2 Me30:ZSM5-50H 0.05-0.1 70.59 1.89 48.39 49.370.35 8:2 C3 Me30:ZSM5-100H 0.05-0.1 73.46 1.06 49.09 49.23 0.63 8:2 C4Me30:ZSM5-400H 0.05-0.1 15.92 96.2 0.44 1.33 2.03 8:2 C5 Me30:ZSM5-100H0.05-0.1 73.46 1.06 49.09 49.23 0.63 8:2 C6 Me30:ZSM5-100H  0.1-0.1565.86 2.86 50.95 46.12 0.07 8:2 E1 Me30:ZSM5-100H 0.15-0.2 81.43 2.9150.22 46.79 0.08 8:2 E2 Me30:ZSM5-100H  0.2-0.5 79.43 1.91 51.88 48.170.08 8:2 C7 Me30:ZSM5-100H  0.5-0.7 61.88 3.76 48.69 47.67 0.07 8:2 E3Pellet from E1 3 × 3 mm 80.78 1.73 49.17 48.89 0.21 All gaseous streamswere analyzed via online-GC. Argon was used as internal standard tocorrelate in and off gas streams. CO conversion is given as follows:(CO_(in) − (CO_(out) * Argon_(in)/Argon_(out)))/CO_(in) * 100% S(MeOH) =Volume (MeOH) in product stream/Volume (MeOH + DME + CO₂ + Otherswithout hydrogen and CO) in product stream * 100% S(DME) = Volume (DME)in product stream/Volume (MeOH + DME + CO₂ + Others without hydrogen andCO) in product stream * 100% S(CO₂) = Volume (CO₂) in productstream/Volume (MeOH + DME + CO₂ + Others without hydrogen and CO) inproduct stream * 100% S(Others) = Volume (Others) in productstream/Volume (MeOH + DME + CO₂ + Others without hydrogen and CO) inproduct stream * 100% “Others” are compounds that are formed out of H₂and CO in the reactor that are not MeOH, DME, or CO₂.

TABLE 2 D-10 [μm] D-50 [μm] D-90 [μm] Me30 (0.05-0.1) 2.42 46.57 89.14Me30 (0.1-0.15) 5.06 129.53 143.06 Me30 (0.15-0.2) 6.33 131.69 189.23Me30 (0.2-0.5) 20.71 275.6 396.86 ZSM5-100H (0.05-0.1) 2.87 56.38 82.17ZSM5-100H (0.1-0.15) 5.47 100.92 184.78 ZSM5-100H (0.15-0.2) 5.27 163.57196.22 ZSM5-100H (0.2-0.5) 5.15 373.09 489.57

The invention claimed is:
 1. Catalytically active body for the synthesisof dimethyl ether from synthesis gas, comprising a mixture of: (A)70-90% by weight of a methanol-active component, selected from the groupconsisting of copper oxide, aluminium oxide, zinc oxide, amorphousaluminium oxide, ternary oxide or mixtures thereof, (B) 10-30% by weightof an acid component, selected from the group consisting ofaluminosilicate, γ-alumina and zeolite or mixtures thereof, (C)0-10Gew.-% by weight of at least one additive, whereby the sum of thecomponents (A), (B) and (C) is in total 100% by weight.
 2. Catalyticallyactive body according to claim 1, whereby the component (A) has aparticle size distribution characterized by a D-10 value of 5-140 μm, aD-50 value of 40-300 μm, and a D-90 value of 180-800 μm, whereby thecomponent (B) has a particle size distribution characterized by a D-10value of 5-140 μm, a D-50 value of 40-300 μm, and a D-90 value of180-800 μm and the particle size distribution of components (A) and (B)is maintained in the catalytically active body.
 3. Catalytically activebody according to claim 1, characterized in that component (A) comprises50-80% by weight of copper oxide, 15-35% by weight of ternary oxide and15-35% by weight of zinc oxide and the sum of which is in total 100% byweight.
 4. Catalytically active body according to claim 1, characterizedin that component (A) comprises 50-80% by weight of copper oxide, 2-8%by weight of aluminium oxide, wherein the aluminium oxide is boehmiteand 15-35% by weight of zinc oxide and the sum of which is in total 100%by weight.
 5. Catalytically active body according to claim 1,characterized in that component (A) comprises 50-80% by weight of copperoxide, 2-8% by weight of amorphous aluminium oxide and 15-35% by weightof zinc oxide and the sum of which is in total 100% by weight. 6.Catalytically active body according to claim 1, characterized in thatcomponent (A) comprises 50-80% by weight of copper oxide, 2-8% by weightof aluminium oxide and 15-35% by weight of zinc oxide and the sum ofwhich is in total 100% by weight.
 7. Catalytically active body accordingto claim 1, wherein the zeolite comprises 35-55% by weight of silicon,0.15-4% by weight of aluminium, 45-65% by weight of oxygen and whereappropriate 0-0.3 by weight of sodium and the sum of which is in total100% by weight.
 8. Catalytically active body according to claim 1,wherein the catalytically active body consists of (A) 70-90% by weightof a methanol-active component and 10-30% by weight of a zeolite (B) andthe sum of (A) and (B) being in total 100% by weight.
 9. Catalyticallyactive body according to claim 1, wherein the catalytically active bodyis a pellet with a size in the range from 1×1 mm to 10×10 mm.
 10. Methodfor the preparation of dimethyl ether from synthesis gas comprising atleast the steps: a) reducing the catalytically active body as defined inclaim 1, b) contacting the catalytically active body in a reduced formwith hydrogen and at least one of carbon monoxide or carbon dioxide. 11.Method for the preparation of a catalytically active body, comprisingthe step: c) preparation of a physical mixture comprising: (A) 70-90% byweight of a methanol-active component, selected from the groupconsisting of copper oxide, aluminium oxide, zinc oxide, amorphousaluminium oxide, ternary oxide or mixtures thereof, (B) 10-30% by weightof an acid component, selected from the group consisting ofaluminosilicate, γ-alumina and zeolite or mixtures thereof, (C) 0-10Gew.-% by weight of a at least one additive, whereby the sum of thecomponents (A), (B) and (C) is in total 100% by weight.
 12. Method forthe preparation of a catalytically active body according to claim 11,whereby the component (A) has a particle size distribution characterizedby a D-10 value of 5-140 μm, a D-50 value of 40-300 μm, and a D-90 valueof 180-800 μm, whereby the component (B) has a particle sizedistribution characterized by a D-10 value of 5-140 μm, a D-50 value of40-300 μm, and a D-90 value of 180-800 μm and the particle sizedistribution of components (A) and (B) is maintained in thecatalytically active body.
 13. Method for the preparation of acatalytically active body according to claim 11, comprising further thesteps: a) precipitation a copper-, zinc,- or aluminium salt or a mixturethereof, b) calcination of the product obtained in step a).
 14. Methodfor the preparation of a catalytically active body according to claim11, wherein a pellet is formed.
 15. Method for the preparation of acatalytically active body according to claim 11, wherein the components(A) and (B) are independently pressed through at least one sieve,whereby the sieve exhibits a mesh size from 0.005 to 5 mm in order toobtain a particle size distribution characterized by a D-10 value of5-140 μm, a D-50 value of 40-300 μm, and a D-90 value of 180-800 μm. 16.Method for the preparation of a catalytically active body according toclaim 11, wherein at least three different sieves are used, whereby thecomponents (A) and (B) are pressed in direction from the sieve with thebiggest mesh size to the sieve with the smallest mesh size.
 17. Methodfor the preparation of a catalytically active body according to claim11, wherein in step a) at least a part of the component (A) is preparedby precipitation reaction and/or calcination.
 18. Method for thepreparation of a catalytically active body according to claim 11,whereby at least one part of component (A) is precipitated and wherebyat least another part of component (A), which is not subjected to thefirst precipitation, is added to the precipitate.
 19. Method for thepreparation of a catalytically active body according to claim 11,wherein the method further comprises the step d) adding a mixture ofhydrogen and nitrogen to component (A) and/or (B).